The present invention relates to (1) a process for the production of a low-molecular-weight allylamine polymer or an addition salt thereof, (2) a low-molecular-weight allylamine polymer or an addition salt thereof, (3) a water-resistance-imparting agent for use in an ink, which contains the same, and (4) an ink composition containing the above water-resistance-imparting agent. More specifically, it relates to (1) a process for efficiently and industrially advantageously producing a low-molecular-weight allylamine polymer or an addition salt thereof, which is improved in coloring, has little ignition residue content and is useful for use in various fields, (2) a low-molecular-weight allylamine polymer or an addition salt thereof, of which the ignition residue content, the unreacted monoallylamine content and the coloring are small or low and which is useful for various uses in the field of fine chemicals, (3) a water-resistance-imparting agent for use in an ink, which contains a low-molecular-weight allylamine polymer or its addition salt having the above properties and which is suitable for use in an inkjet recording ink, and (4) an ink composition, particularly an inkjet recording ink composition, which contains the above water-resistance-imparting agent and is excellent in water resistance and shelf life.
It is hitherto known that allylamine does not easily undergo polymerization due to degradative chain transfer, and there is not much that is known concerning any effective method for producing an allylamine polymer. As a general method of producing an allylamine polymer or an addition salt thereof, there is known a method in which a monoallylamine addition salt is polymerized in water or a polar solvent in the presence of a radical polymerization initiator having a molecule containing an azo group and a cationic-nitrogen-possessing group at a temperature in the range of from 40 to 70xc2x0 C., to obtain an addition salt of an allylamine polymer, and optionally, the so-obtained addition salt of an allylamine polymer is neutralized with an alkali (e.g., JP-A-58-201811). An allylamine polymer or an addition salt thereof obtained by the above method is relatively free from being colored, and is used in the fields of dye fixing agents, binders for paper making and additives to various chemicals.
On the other hand, in recent years, a low-molecular-weight allylamine polymer or an addition salt thereof is demanded in a variety of fields. When the radical polymerization initiator having a molecule containing an azo group and a cationic-nitrogen-possessing group is used as a radical polymerization initiator, however, it is required to use a large excess of an inorganic acid such as hydrochloric acid for producing a low-molecular-weight allylamine polymer or an addition salt thereof, as is described in JP-B-6-2780, so that there are involved problems that the removing of an excess of the inorganic acid is complicated and that a polymer solution obtained is liable to be colored.
Further, as another method of producing a low-molecular-weight allylamine polymer or an addition salt thereof, JP-A-5-195450 discloses a method in which an aqueous solution of an addition salt of a monoallylamine is provided and allowed to react in the presence of a large amount of a peroxide-based radical polymerization initiator at a high temperature.
In the above method, however, the radical polymerization initiator is used in a large amount and the polymerization is carried out under severe temperature conditions. There are therefore caused problems that an aqueous solution of an obtained low-molecular-weight allylamine polymer or addition salt thereof is inevitably colored in brown or the like, and that the coloring is liable to proceed with the passage of time.
Further, when a solution prepared by polymerization according to the above method is treated with activated carbon for overcoming the above coloring, procedures of removing the activated carbon by filtration are required. Moreover, a fine powder of the activated carbon is liable to be contained in the end polymer during the filtration, and it sometimes causes a problem in some use.
As a printer, a dot impact printer, a laser printer, a thermal printer, an inkjet printer, etc., are known. Of these, an inkjet printer is widely used in recent years due to characteristic features such as fast printing with a low noise, a low printing cost, downsizing and weight-decreasing feasibility based on a simple mechanism, an easiness in multi-color printing and image size increasing, non-necessity of development and fixing and adaptability of a record pattern.
In the above inkjet printer, conventionally, recording is carried out by an inkjet recording method in which an ink blob is generated and ejected by an electrostatic suction method, an air compression method, a method using electric deformation of a piezoelectric element or a method using a pressure caused by heat-blowing, and further, the ink blob is allowed to adhere to a recording paper. As an ink for use with the above recording method, generally, there is used a water-based ink prepared by dissolving or dispersing a colorant such as a dye or a pigment in water, a water-soluble organic solvent or a mixture of these.
In recent years, inkjet recording is required to satisfy water resistance on an ordinary paper, and as a water-based ink composition for attaining the above requirement, combinations of polyethyleneimine and polyamlines mainly including modified products thereof with dyes have been studied in various ways.
For example, there have been proposed (1) a water-fast inkjet composition comprising a hydroxyethylated polyethyleneimine and a dye component (JP-A-62-119280), (2) a water-resistant water-based ink composition comprising a polyamine having a molecular weight of at least 300 and having primary amino groups, an anionic dye, a stabilizer and a wetting agent (JP-A-2-255876 and JP-A-3-188174) and (3) a water-based ink comprising a specific anionic dye and amino acid type polyamine or polyethyleneimine (JP-A-8-113743).
However, the inkjet composition in the above (1) has a problem that since polyethyleneimine contains hydroxyethyl groups and hydrophilic nature increases depending upon the degree of a content thereof, so that water resistance decreases. The water-based ink composition in the above (2) involves a problem that a shelf life is poor since polyethyleneimine specifically described in Example highly possibly attacks an anionic dye. Further, the water-based ink in the above (3) has a problem that it is required to select a dye suitable for imparting water resistance from an anionic metal-containing dye, a metal-free dye having an anionic group and an azo group in specific positions or a metal-free azo dye having an aromatic ring, which limits dye selection to a narrow range, so that it is difficult to prepare an ink having a desired hue and a desired color density.
On the other hand, attempts have been made to use an allylamine polymer as a water-resistance-imparting agent in an ink composition. In this case, however, there are required complicated procedures of reacting an allylamine hydrochloride polymer with a dye (dye containing acid salt such as sulfonic acid salt, etc.) to prepare a dye containing an allylamine polymer as a counter cation and removing an inorganic salt, etc., by isolating it as a solid before use, as is described in JP-A-63-33484. Further, for avoiding the above complicated procedures, an allylamine polymer is converted to a free polymer in advance, and further, an inorganic salt, etc., are removed. Even in this case, when the allylamine polymer is used in an ink, the ink is liable to cause aggregation, which causes a problem in use.
Under the circumstances, a first object of the present invention is to provide a process for efficiently and industrially advantageously producing a low-molecular-weight allylamine polymer or its addition salt, which is improved in coloring, has little ignition residue content and is useful for various fields.
A second object of the present invention is to provide a low-molecular-weight allylamine polymer or its addition salt, which has a high quality and is useful for various uses in the field of fine chemicals.
Further, a third object of the present invention is to provide a novel water-resistance-imparting agent for use in an ink, which is suitable for use in an inkjet recording ink, and a fourth object of the present invention is to provide an ink composition, particularly an inkjet recording ink composition, which contains the above water-resistance-imparting agent and is excellent in water resistance and shelf life.
For achieving the above objects, the present inventors have made diligent studies and as a result, have found that the first object can be accomplished by distilling a low-molecular-weight allylamine polymer solution containing an unreacted monoallylamine and salt to distill off the unreacted monoallylamine, then subjecting the residue to electrodialysis, and optionally, further carrying out acid treatment.
Further, it has been found that a low-molecular-weight allylamine polymer having an ignition residue content equivalent to, or lower than, a specific value, having a weight average molecular weight in a specific range and preferably having an unreacted monoallylamine content and an absorbance, measured by a certain method, which are equivalent to, or smaller than, specific values, or an addition salt of a low-molecular-weight allylamine polymer having the above properties can meet the second object, that a water-resistance-imparting agent containing a low-molecular-weight allylamine polymer having the above properties or an addition salt thereof can meet the third object, and further that an ink composition comprising a low-molecular-weight allylamine polymer having the above properties or an addition salt thereof can meet the fourth in object.
The present invention has been made on the basis of the above findings.
That is, the first object of the present invention is achieved by a process for the production of a low-molecular-weight allylamine polymer having a weight average molecular weight of 250 to 4,000 or an addition salt thereof, which comprises distilling a low-molecular-weight allylamine polymer solution containing an unreacted monoallylamine and a salt, thereby distilling off the unreacted monoallylamine, then, subjecting a residue to electrodialysis, and optionally carrying out acid treatment.
Further, the second object of the present invention is achieved by a low-molecular-weight allylamine polymer having an ignition residue content of 5% by weight or less and a weight average molecular weight of 250 to 4,000, or an addition salt of a low-molecular-weight allylamine polymer having the above properties.
Furthermore, the third object of the present invention is achieved by a water-resistance-imparting agent for an ink, comprising a low-molecular-weight allylamine polymer having an ignition residue content of 5% by weight or less and a weight average molecular weight of 250 to 4,000, or an addition salt of a low-molecular-weight allylamine polymer having the above properties.
Moreover, the fourth object of the present invention is achieved by an ink composition comprising (A) a colorant and (B) a water-resistance-imparting agent containing a low-molecular-weight allylamine polymer having an ignition residue content of 5% by weight or less and a weight average molecular weight of 250 to 4,000, or an addition salt of a low-molecular-weight allylamine polymer having the above properties.